In a process of designing two-axis and three-axis magnetic compass chips, it is necessary to use X-axis and Y-axis magnetic sensors at the same time. A magnetoresistive sensing unit usually has a single magnetic field sensing axis, for example, has a magnetic sensing axis in an X direction. For providing a magnetic sensing axis in a Y direction, it is common to rotate the X-direction magnetic field sensing unit by 90 degrees, to accordingly obtain a Y-direction magnetic field sensing unit. Next, in order to improve magnetic field sensitivity of the X-axis and Y-axis magnetoresistive sensors, a push-pull bridge is generally adopted, wherein a push arm and a pull arm are manufactured in a discrete manner, that is, one of them is rotated by 180 degrees relative to the other. In this way, the push arm and the pull arm have opposite pinning layer magnetization directions, while having identical freelayer magnetization directions. For example, FIG. 2a is a schematic diagram of a magnetization state of magnetoresistive sensing units with pinning layers of such wire-bond type, wherein the push arm chips and the pull arm chips are connected using wire-bonds.
The Y-axis magnetoresistive sensor proposed above mainly has the following problems:
1) When X-axis and Y-axis magnetoresistive sensors are prepared on a same plane at the same time, as the X-axis and Y-axis magnetoresistive sensors are both discrete elements, it is impossible to implement integrated manufacturing, thus increasing complexity of the process and affecting measurement precision of the two-axis or three-axis sensor.
2) The push arms and the pull arms cannot be integrated on the same chip, and it is necessary to connect discrete chips using wire-bonds which increases the complexity of the process and affects the measurement precision of the sensor.